This invention relates to printing equipment in general and, more specifically, is addressed to a new and improved screen printing machine which is readily adapted to print on objects of various shapes.
Stencil screen printing in the past was known as silk screen printing because of the use of silk as the material for the stencil screen. Even though modern fabrics made the use of silk obsolete, stencil screen printing is still sometimes referred to as silk screen printing. The technology is relatively simple: A printing fluid, such as ink, is transferred to the surface to be printed by means of a squeegee, which forces the ink through a stencil screen having certain areas open, with other areas blocked off, thereby forming the desired design. A wide variety of objects may be printed with the screen printing technique, such as clock dials; ash trays; irregular objects such as plates, cups and coffee pots; and flatwork such as glass and glass thermometers, to mention a few. The applications of screen printing are widespread and continue to increase each year.
Where several different colors are printed, registration of the object to be printed and repeatability of the print is essential for a high-quality multi-color product. In printing flatwork, the screen is held stationary and the squeegee moves across the screen to force the ink through the screen onto the object to define the chosen pattern. Obviously, in this application it is desirable to have the object to be printed in rigid attachment and bring the screen and squeegee to the work. In the printing of irregular objects, such as conical, curvilinear, or cylindrical objects, the squeegee remains stationary and continually biased on the screen, which screen moves simultaneously and at the same linear rate as the circumferential speed of the object to be printed. As before, the squeegee forces the ink through selected areas on the screen to form on the irregular object. One example of such type of printing is a cylindrical pail or drum bearing a message or design. Also, many types of household cylinders formed of plastic by the blow-molding process carry messages and designs. All of the above flat and irregular objects may be imprinted on a machine of the type described herein.